Grounding cables

Abstract

A grounding device (1) for a cable, comprising an elongate body of a conductive material, the elongate body having a length, the body comprising: a long portion (2) having locking features; and a latch portion (3), in which the latch portion (3) is arranged to receive the long portion (2) and to engage locking features on the long portion (2) such that the body forms a loop and the latch portion (3) resists removal of the long portion (2) from the latch portion (3), with an extending part of the long portion (2) extending out of the latch portion (3) when the long portion (2) is received in the latch portion (3). Typically, the long portion (2) and / or the body will be formed as a flat strip, which can be bent in order for the long portion (2) to engage the latch portion (3).

Description

[0001] GROUNDING CABLES

[0002] This invention relates to grounding devices for cables, cables, cable glands, and methods of grounding cables.

[0003] Cable glands are well known for use in passing cables through the walls of enclosures, particularly of electrical equipment.

[0004] Some electrical equipment requires that cables entering that equipment is shielded against leaking of electro-magnetic radiation - so called EMC or “electromagnetic compatibility” screening. As such, it is sometimes required to ground the screening conductor that is part of the cable and surrounds the useful cores of the cable. Prior art methods of doing so have largely been manually intensive or impossible to fit retrospectively.

[0005] As such, in a first aspect of the invention, we provide a grounding device for a cable, comprising an elongate body of a conductive material, the elongate body having a length, the body comprising:

[0006] a long portion having locking features; and

[0007] a latch portion,

[0008] in which the latch portion is arranged to receive the long portion and to engage locking features on the long portion such that the body forms a loop and the latch portion resists removal of the long portion from the latch portion, with an extending part of the long portion extending out of the latch portion when the long portion is received in the latch portion.

[0009] As such, this defines a grounding device which, by being formed of a conductive material will inherently form an electrical contact when in contact with the shield of a shielded cable received within the loop, with the loop inherently retaining the grounding device onto the cable; the extending part can then contact the inside of a cable gland or the like so that the cable gland is also in electrical contact with the shield (and so is, in normal use, grounded).

[0010] Typically, the long portion and / or the body will be formed as a flat strip, which can be bent in order for the long portion to engage the latch portion. The conductive materialmay be resilient, in that when bent from a flat state to a bent state, it elastically tends to revert to the flat state.

[0011] The conductive material may comprise a metal, metallic or conductive material, such as brass, copper or other non magnetic metal. Material may also take the form of a polymeric material loaded with conductive material such as carbon loaded rubber.

[0012] The locking features may comprise a plurality of slots formed in the long portion, with the slots being spaced apart along the length; having a plurality of slots spaced apart along the length allows for different diameter cables to be grounded as the latch portion can engage different slots along the length, thus changing the circumference and so diameter of the loop.

[0013] The latch portion may comprise a latch slot having a tab extending into the latch slot, with the tab being arranged to engage the locking features, especially the slots. As such, the long portion can be inserted into the latch slot to form the loop; continued passage of the long portion through the latch slot will decrease the circumference and so the diameter of the loop. The tab may form a pawl and the slots a ratchet, such that the pawl allows the long portion to be inserted into the latch slot, but resists its withdrawal therefrom.

[0014] According to a second aspect of the invention, there is provided a cable having at least one conductive core and a grounding sheath around the at least one core, in which there is provided a grounding device in accordance with the first aspect of the invention in which the long portion has been inserted into the latch portion to form a loop, in which the loop surrounds the cable and in which the elongate body is in contact with the grounding sheath.

[0015] The cable may comprise outer insulation covering the grounding sheath; this may not be present over a location where the elongate body is in contact with the grounding sheath. There may be an extending portion of the long portion extending from the latch; this may be at least 1cm, 2cm, 3cm, 4cm or 5cm long, or at least as long as the circumference of the cable at the location.The location where the elongate body is in contact with the grounding sheath may comprise at least 50%, 75%, 90%, 99% or 100% of a circumference of the grounding sheath around the cable.

[0016] According to a third aspect of the invention, there is provided a combination of the cable of the second aspect of the invention and a cable gland having a body defining an internal bore through which the cable passes, the cable gland sealing onto the cable, the cable gland body being formed of a conductive material, in which the grounding device is in contact with the body of the cable gland.

[0017] As such, this provides a simple means of grounding a cable in a cable gland. Typically, the body of the cable gland will be electrically connected to a ground.

[0018] The cable gland body may be formed of a metal or a metallic material, such as brass.

[0019] According to a fourth aspect of the invention, there is provided a method of grounding a cable having at least one conductive core and a grounding sheath around the at least one core, the method comprising passing the grounding device of the first aspect of the invention around the grounding sheath and passing the long portion through the latch portion so that the elongate body contacts the grounding sheath and the locking portion engages the locking features.

[0020] The method may comprise exposing the grounding sheath at a location where the grounding device is to contact the grounding sheath. The step of exposing the grounding sheath may comprise removing insulation over the grounding sheath.

[0021] The method may comprise passing the cable through an internal bore in a body of cable gland, the body being formed of conductive material. The method may comprise the cable gland sealing onto the cable. The method may comprise the grounding device, and particularly the long portion and especially a portion of the long portion that extends through the latch portion, contacting the body of the cable gland. The method may also comprise grounding the body of the cable gland.As such, this method may comprise retrofitting the grounding device in the cable gland; as such, the cable gland may not have originally been provided with the grounding device.

[0022] According to a fifth aspect of the invention, there is provided a grounding device for a cable, comprising a cylindrical body surrounding a bore, and a plurality of teeth extending from the cylindrical body into the bore; the teeth and the cylindrical bore being at least partially if not totally formed of a conductive material.

[0023] As such, by making use of a cylindrical body, the device can be inserted into the bore of a cable gland, either from manufacturer assembly or retrospectively, which are typically formed of metallic materials such as brass, and which can be grounded. The teeth can make contact with a grounding shield of a cable which is passed through the bore of the grounding device and of the cable gland, to ensure electrical continuity between the grounding shield and the cable gland.

[0024] As such, the grounding device could be formed of metal or a metallic material. Alternatively, it could be formed of a polymeric material loaded with conductive material, such as carbon or iron loaded rubber.

[0025] The teeth may deform elastically relative to the cylindrical body, such that when a cable is inserted into the bore of the grounding device, the teeth bias against the cable. This is easy to achieve in both metallic and polymeric materials.

[0026] According to a sixth aspect of the invention, there is provided a cable having at least one conductive core and a grounding sheath around the at least one core, in which there is provided a grounding device in accordance with the fifth aspect of the invention, in which the cable passes through the bore of the grounding device and the teeth are in contact with the grounding sheath of the cable.

[0027] The cable may comprise outer insulation covering the grounding sheath; this may not be present over a location where the elongate body is in contact with the grounding sheath.According to a seventh aspect of the invention, there is provided a combination of the cable of the sixth aspect of the invention and a cable gland having a body defining an internal bore through which the cable passes, the cable gland sealing onto the cable and being formed of a conductive material, in which the grounding device is received within the bore of the cable gland and is in contact with the body of the cable gland.

[0028] As such, this provides a simple means of grounding a cable in a cable gland. Typically, the body of the cable gland will be electrically connected to a ground.

[0029] The cable gland body may be formed of a metal or a metallic material, such as brass.

[0030] The cylindrical body of the grounding device may be an interference fit within the bore of the cable gland. This is sufficient to provide the grounding function.

[0031] There now follows, by way of example only, description of embodiments of the invention, described with reference to the accompanying drawings, in which:

[0032] Figure 1 shows a plan view of a grounding device in accordance with a first embodiment of the invention;

[0033] Figure 2 shows a plan view of a grounding device in accordance with a second embodiment of the invention;

[0034] Figure 3 shows a perspective view of the grounding device of Figure 1 fitted onto a cable;

[0035] Figure 4 shows a perspective view of the grounding device of Figure 3 on the cable of Figure 3 installed into a cable gland;

[0036] Figures 5a to 5c show plan views of grounding devices of three further embodiments of the invention;

[0037] Figure 6 shows a cut-away perspective view of a grounding device installed in a cable gland in accordance with a third embodiment of the invention;Figure 7 shows a perspective view of the grounding device of Figure 6;

[0038] Figure 8 shows a cut-away perspective view of a grounding device installed in a cable gland in accordance with a fourth embodiment of the invention;

[0039] Figure 9 shows a perspective view of the grounding device of Figure 8;

[0040] Figures 10 to 12 show side elevations of alternative versions of the grounding device of Figure 8;

[0041] Figure 13 shows a perspective view of the metal part of a grounding device in accordance with a fifth embodiment of the invention;

[0042] Figure 14 shows a perspective view of the grounding device of Figure 13, including a rubber overmoulding; and

[0043] Figures 15a to 15c show plan views of grounding devices of three further embodiments of the invention.

[0044] A grounding device 1 for a cable in accordance with a first embodiment of the invention is shown in Figure 1 of the accompanying drawings. The device 1 comprises an elongate body having a length (horizontal in Figure 1) formed of non-magnetic stainless steel (and hence conductive), which has a long portion 2 and a latch portion 3. The latch portion 3 comprises a tab 4 in a slot 5, the slot being wide enough (vertically in Figure 1) to receive the width of the long portion 2.

[0045] The long portion 2 has a series of slots 6 spaced along its length. As such, if the end 7 of the long portion 2 is inserted into the slot 5 of the latch portion 3, then the tab 4 will act as a pawl with the slots 6 in the long portion 2 action as a ratchet, allowing passage of the long portion 2 through the latch portion 3, but resisting withdrawal of the long portion 2 from the latch portion 3. As such, the grounding device can be used to form a loop, which will start at a circumference of the distance from the end 7 to the latch portion 3, and then decrease as the long portion 2 is passed through the latch portion 3.The slots also act to conform the material around a circular cable diameter, providing extra flexibility.

[0046] The utility of this can be seen in Figures 3 and 4 of the accompanying drawings. In these figures, the grounding device 1 is being used to ground a cable 10. The cable 10 comprises cores 11 surrounded by insulation 12 which is in turn surrounded by a conductive grounding sheath 13. Outer insulation 14 completes the cable 10.

[0047] As shown in Figure 3, the outer insulation 14 has been cut away over a portion 15 of the cable 10 to expose the grounding sheath 13. The grounding device 1 has been looped around the cable 10 so that the cable 10 is received within the loop of the grounding device 1 and drawn tight. As such, the grounding device 1 acts in a similar manner to a cable tie and securely contacts the grounding sheath 13. Because the grounding sheath 13 is formed of a conductive material, there is electrical continuity from the grounding sheath 13 along the cable 10 into the grounding device 1.

[0048] In Figure 4, the cable 10 and grounding device 1 have been installed in the internal bore 21 of a cable gland 20, which has a body 22 formed of brass (which is both metallic and conductive). The long portion 2, and in particular the end 7 are in contact with the body 22 of the cable gland 20. As such, the electrical continuity discussed above will extend from the grounding sheath 13 through the grounding device 1 to the cable gland 20. Because stainless steel is resilient or “springy”, the long portion 2 will be biassed into contact with the internal surface of the bore 21 to ensure a good contact.

[0049] Figures 5a to 5c show a set of sizes of different grounding devices that can be used to ground a wide range of cable diameters (from 5mm to 32mm). The grounding device 51 in Figure 5a is 46.25mm long, and can be used to ground cables of 5mm to 12mm. The grounding device 52 in Figure 5b is 72.75mm long, and can be used to ground cables of 5mm to 19mm. The grounding device 53 in Figure 5c is 116mm long, and can be used to ground cables of 15mm to 32mm. All of the devices have the same slot pitch of 1 ,5mm.

[0050] Figures 15a to 15c show another set of grounding devices that can be used to ground a cable, as described above. Much like the grounding devices of Figures 5a to 5c, the grounding devices of Figures 15a to 15c vary in length such that they can be used toground a wide range of cable diameters. The grounding device 501 of Figure 15c is particularly long, being longer than that of Figure 5c. For example, the grounding device of Figure 15c may be at least 150mm long, and optionally at least 175mm, 200mm, or 225mm long.

[0051] As for the grounding devices 51, 52, 53 of Figures 5a to 5c, the grounding devices 301, 401, 502 of Figures 15a to 15c comprise an elongate body having a long portion 302, 402, 502 and a latch portion 303, 403, 503. The latch portion comprises a tab 304, 404, 504 in a slot 305, 305, 505, the slot being wide enough to receive the width of the long portion. The long portion has a series of slots 306, 406, 506 spaced along its length, so that the grounding device can be used to form a loop as described above.

[0052] The width of each slot 306, 406, 506 of the grounding devices 301, 401, 501 may be narrower than those of the grounding devices of Figures 5a to 5c. The grounding devices 301, 401, 501 may therefore have an increased number of slots 306, 406, 506 per unit length, as compared to the grounding devices of Figures 5a to 5c. Increasing the number of slots per unit length may advantageously increase the adjustability of the device, allowing the diameter of the eventual loop to be set in smaller increments. This may allow the device to sit more snugly around the cable, resulting in a more secure and reliable fit.

[0053] As a result of the reduced slot width in grounding devices 301, 401, 501, the width of the tabs 304, 404, 504 may accordingly be less than those of grounding devices 51, 52, 53.

[0054] The grounding devices of Figures 15a to 15c may otherwise be substantially identical to those of Figures 5a to 5c (i.e. differing only in their length, slot width and tab width, as described above).

[0055] As such, rather than having to provide a different device for each diameter of cable, using a grounding device of the form described allows for a wide range of cable diameters to be grounded.

[0056] There is no risk of getting fingers stuck in the gland if it the grounding device is mishandled, no risk of clips flying off, and due to the material, is not effected by eddy currents. The grounding device is incredibly sympathetic to the cable screening.Due to the component being a “pull-through tie” it can be fitted to the gland prior or post assembly onto the cable. In other words, it can be fitted on primary installation or retro fitted without requiring disassembly of the gland, should an EMC compliant cable gland be required.

[0057] The second embodiment of the invention shown in Figure 2 of the accompanying drawings, has, in addition to the slots 36, crescent shaped tabs 40 to better grip the cable. The “rear” end of the body of the grounding device 37 (to the right of the latching portion 38), is plain with no slots, providing a pull tab for a user.

[0058] Figures 6 and 7 of the accompanying drawings show a grounding device 101 in accordance with a third embodiment of the invention. The grounding device 101 is formed of sheet metal (in particular, copper).

[0059] The grounding device 101 comprises a cylindrical body 102 surrounding an internal bore 103 and a plurality of teeth 104 extending into the bore 103. As the material of the grounding device is elastic, the teeth 104 will also be resilient (or “springy”) and so will tend to return towards the position shown in Figure 7, when the teeth roughly speaking lie on the surface of a conic frustum, so that there is a smaller aperture 105 defined by the end of the teeth 104 (and so forming one end surface of the frustum).

[0060] As such, a cable can be passed through the internal bore. As long as the cable and cable grounding sheath is of greater diameter than the aperture 105, doing so will force the teeth 104 apart, which will then apply a biasing force against the surface of the cable. If the outer insulation of the cable is stripped back as with the previous embodiments, the teeth will bias against the grounding shield of the cable, providing electrical continuity between the grounding shield and the grounding device 101.

[0061] As the outer surface of the grounding device 101 is cylindrical (i.e. is the cylindrical body 102), it can be fitted within the bore of a cable gland 120 as shown in Figure 6 of the accompanying drawings. If the cable gland 120 is, as is customary, metallic, such as brass, then electrical continuity will be provided from grounding shield through teeth 104 (which do not extend out of the bore of the cable gland 120), cylindrical body 102 to the cable gland 120. It is an interference fit within the bore of the cable gland so that it cannot be easily removed.A fifth aspect of the invention is shown in Figures 8 and 9 of the accompanying drawings. In this embodiment, the grounding device 151 is formed of a conductive rubber rather than of metal, for example rubber loaded with metallic material such as iron, or rubber loaded with carbon or other non-metallic conductive material. It otherwise functions in the same manner as the previous embodiment, with teeth 152 also being provided with a web 153 between them, so as to improve the contact between a cable inserted in the aperture 154 and the teeth 152 or web 153.

[0062] Alternative variants of the grounding device are shown in Figures 10 to 12. A variant with a plain outer surface 160 is shown in Figure 10. A variant with a flange 161 at one end for locating the grounding device in the cable gland 160 is shown in Figure 11. A further variant is shown in Figure 12 which in addition has exterior ribs 162 for better engagement with the internal bore of the cable gland.

[0063] A sixth aspect of the invention is shown in Figures 13 and 14 of the accompanying drawings. This comprises a grounding device 200 comprising a metal component 201 having a cylindrical body 202 and teeth 203 as in the fourth embodiment. Over the teeth 203, there has been overmoulded a conductive rubber overmoulding 204, so as to still provide electrical continuity but also to enabling contact with more delicate grounding shields that might not otherwise withstand direct engagement with the teeth of the fourth embodiment.

Claims

CLAIMS1. A grounding device for a cable, comprising an elongate body of a conductive material, the elongate body having a length, the body comprising:a long portion having locking features, the locking features comprising a plurality of slots formed in the long portion, with the slots being spaced apart along the length; anda latch portion,in which the latch portion is arranged to receive the long portion and to engage locking features on the long portion such that the body forms a loop and the latch portion resists removal of the long portion from the latch portion, with an extending part of the long portion extending out of the latch portion when the long portion is received in the latch portion.

2. The grounding device of claim 1, in which the long portion and / or the body are formed as a flat strip which can be bent in order for the long portion to engage the latch portion.

3. The grounding device of claim 1 or claim 2, in which the conductive material is resilient.

4. The grounding device of any preceding claim, in which the latch portion comprises a latch slot having a tab extending into the latch slot, with the tab being arranged to engage the locking features.

5. The grounding device of claim 4, in which the tab forms a pawl and the slots form a ratchet, such that the pawl allows the long portion to be inserted into the latch slot, but resists its withdrawal therefrom.

6. A cable having at least one conductive core and a grounding sheath around the at least one core, in which there is provided a grounding device in accordance any preceding claim, in which the long portion has been inserted into the latch portion to form a loop, in which the loop surrounds the cable and in which the elongate body is in contact with the grounding sheath.

7. The cable of claim 6, comprising outer insulation covering the grounding sheath, which is not present over a location where the elongate body is in contact with the grounding sheath.

8. A combination of:a cable anda cable gland having a body defining an internal bore through which the cable passes,in which the cable has at least one conductive core and a grounding sheath around the at least one core, and is provided with a grounding device,the grounding device comprising an elongate body of a conductive material, the elongate body having a length, the body comprising:a long portion having locking features; anda latch portion,in which the latch portion is arranged to receive the long portion and to engage locking features on the long portion such that the body forms a loop and the latch portion resists removal of the long portion from the latch portion, with an extending part of the long portion extending out of the latch portion when the long portion is received in the latch portion;in which the long portion has been inserted into the latch portion to form the loop, in which the loop surrounds the cable and in which the elongate body is in contact with the grounding sheath, in which the cable gland seals onto the cable, the cable gland body being formed of a conductive material, in which the grounding device is in contact with the body of the cable gland.

9. A method of grounding a cable having at least one conductive core and a grounding sheath around the at least one core, the method comprising passing the grounding device of any of claims 1 to 5 around the grounding sheath and passing the long portion through the latch portion so that the elongate body contacts the grounding sheath and the locking portion engages the locking features.

10. A method of grounding a cable having at least one conductive core and a grounding sheath around the at least one core using a grounding device, the grounding device comprising an elongate body of a conductive material, the elongate body having a length, the body comprising:a long portion having locking features; anda latch portion,in which the latch portion is arranged to receive the long portion and to engage locking features on the long portion such that the body forms a loop and the latch portion resists removal of the long portion from the latch portion, with an extending part of the long portion extending out of the latch portion when the long portion is received in the latch portion;the method comprisingpassing the grounding device around the grounding sheath and passing the long portion through the latch portion so that the elongate body contacts the grounding sheath and the locking portion engages the locking features: andpassing the cable through an internal bore in a body of cable gland, the body being formed of conductive material.

11. The method of claim 10, comprising the grounding device contacting the body of the cable gland.

12. The method of any of claims 10 to 11, comprising grounding the body of the cable gland.

13. The method of any of claims 10 to 12, comprising retrofitting the grounding device in the cable gland.

14. A grounding device for a cable, comprising a cylindrical body surrounding a bore, and a plurality of teeth extending from the cylindrical body into the bore; the teeth and the cylindrical bore being at least partially if not totally formed of a conductive material.

15. The grounding device of claim 14, formed of at least one of metal or metallic material, and polymeric material loaded with conductive material.

16. The grounding device of any of claims 14 or 15, in which the teeth deform elastically relative to the cylindrical body, such that when a cable is inserted into the bore of the grounding device, the teeth bias against the cable.

17. A cable having at least one conductive core and a grounding sheath around the at least one core, in which there is provided a grounding device in accordance with any of claims 14 to 16, in which the cable passes through the bore of the grounding device and the teeth are in contact with the grounding sheath of the cable.

18. A combination of the cable of claim 17 and a cable gland having a body defining an internal bore through which the cable passes, the cable gland sealing onto the cable and being formed of a conductive material, in which the grounding device is received within the bore of the cable gland and is in contact with the body of the cable gland.

19. The combination of claim 18, in which the cylindrical body of the grounding device is an interference fit within the bore of the cable gland.

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